down with black t-shirts

[ChrisH]

Whether something gets hot in the sun or not depends on the ratio of its emmisivity to its absorptivity. The emmisivity is a measure of the ability to radiate energy. The absorptivity is a measure of the ability to absorb energy via radiation. If it absorbs better than it emits and there is a source of radiant energy it will be hotter than the environment. If it emits better than it absorbs it will be the same temperature as the environment, because other methods of heat transfer will make sure of that.

For you REALLY technical types I'm assuming steady state here.

For most things emissivity and absorptivity are assumed to be close to the same. There are special applications where materials are deliberately modified to improve one or the other. They are definitely not dependent on color, though if you're trying to push things one way or the other the materials used can do that for you. (ie it's really hard to make white paint that's loaded with carbon black).

I don't know that anybody has ever measured the relative emissivity and absorptivity of a tee-shirt, let alone a black one. But it might be an interesting experiment. (meaning the results might surprise you) Science fair anyone?

We had the same argument last year. I'm told our school has finally chosen school colors (by executive fiat I think) and we will be using those this year. The bad feelings from last year were a major, though not the only, driver for this.

Two years ago we had gray shirts. When I took a picture of the crowd at Nationals we were easy to find. We were the dull spot way up on the right side. But teams in black didn't show up all that well either.

I've been waiting for a year to try and explain this to someone.

ChrisH